Mystery, she apparently chose the course of hoping he was not telling her the truth.
I don't know how to characterize HOW MUCH it bothered her. Just that of course, it was something that was always there in the back of her mind. Some people put their heads in the sand and are so scared of their own shadow in a situation like that, they become paralyzed to act.
What she should have done is told them in Boulder back when he told her this stuff. Then let THEM worry about whether it was true or not. But she didn't. I swear I've known people who would do the same. I don't get it, but there are people like that.
According to Rita, apparently seeing him arrested and hearing that he's now making these claims to the world, but is being doubted, has given her courage to come forward now (to the Boulder authorities. And Rita has the story, but the woman didn't appear with Rita.)
From your account it does appear that she was/is scared...and only after he's been arrested she had the courage to come forward.......Karr must have been one scary SOB...
What's usually so ironic in scenarios like that is that the people with the most knowledge to contribute to the case don't talk and the ones with the least talk a lot.